JPH07150101A - Cross-linked polyvinyl butyral binder for organic photoconductor - Google Patents

Abstract

PURPOSE: To obtain a self-crosslinked polyvinyl butyral binder component which has excellent mechanical durability, solvent resistance and other properties and is advantageously used for the preparation of org. photoconductors by self-crosslinking polyvinyl butyral by heating or the like.

CONSTITUTION: Polyvinyl butyral is self-crosslinked by heating to about 150 to 300°C or by electron beam irradiation, ultraviolet irradiation, or X-ray irradiation to prepare a self-crosslinked polyvinyl butyral binder component. Next, a photoconductor layer 2 comprising a photoconductor pigment (e.g. a metal-free phthalocyanine pigment) homogeneously distributed in a binder component contg. self-crosslinked polybutyral is formed to a thickness of not less than about 1 μm on a conductive substrate 1 to prepare an org. photoconductor. The org. photoconductor thus obtd. has good charge acceptance, low dark decay, good photodischarge characteristics, and improved adhesion.

COPYRIGHT: (C)1995,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates generally to photoconductors for electrophotography. The present invention provides good speed and stability,
Dry and wet toners are positively chargeable organic photoconductor materials with improved adhesion to multilayer photoconductors for electrophotography.

[0002]

BACKGROUND OF THE INVENTION In electrophotography, a latent image is formed on the surface of a photoconductive material by selectively exposing areas on the charged surface. A difference in electrostatic charge density is created between the areas on the exposed surface and the unexposed surface. A visible image is developed by an electrostatic toner containing a pigment component and a thermoplastic component. These toners
Depending on the relative electrostatic charge of the photoconductor surface, the developing electrode and the toner, it can be selectively deposited on either the exposed photoconductor surface or the unexposed photoconductor surface. The photoconductor may be positively or negatively charged,
Toner systems can also include positively or negatively charged particles. A preferred embodiment for laser printers is that the photoconductor and toner have the same polarity but different charge levels.

In this case, an electrostatic charge opposite to the charge of the toner is applied to the paper sheet or the intermediate transfer medium, and the toner is removed from the photoconductor surface without changing the pattern of the developed image from the photoconductor surface. It is passed near the surface of the photoconductor while being transferred to a sheet of paper or an intermediate transfer medium. After direct transfer or, if an intermediate transfer medium is used, indirect transfer, a set of fusing rollers fixes the toner to the paper to produce a printed image.

Therefore, this important photoconductor surface has been the subject of various research and development in the electrophotographic art. Numerous photoconductor materials have been disclosed as suitable for electrophotographic photoconductor surfaces. For example, amorphous silicon (Si), arsenic selenite (As ₂ Se ₃ ), cadmium sulfide (CdS), selenium (Se), titanium oxide (TiO 2
₂ ) and inorganic compounds such as zinc oxide (ZnO) act as photoconductors. However, these inorganic materials do not meet the current requirements in the electrophotographic art, such as low manufacturing cost, fast response to laser diodes or other light emitting diodes (LEDs), and non-toxic safety.

Therefore, a recent advance in the field of electrophotography on photoconductor surfaces is the organic photoconductor (OP
It is brought about by using organic materials such as C). Typically, the OPCs currently on the market are of the negative charging type and underlie a thicker layer of charge transfer material deposited on the upper surface of the charge generating layer, generally under a thin charge layer, generally less than about 1 micrometer thick. It has a generating material layer. Such a negative charging type OPC exhibits sufficient performance in the case of electrophotographic copying machines and printers for the following applications.

A. Low-end models (4-10 copies per minute) and high-end models (over 50 copies per minute) that use one or two color dry powder developers or liquid developers exclusively for monochrome copying. ) Electrophotographic system.

B. High image quality (over 1800 DPI or more) color proofing system, lithographic plate printing system, and master electrophotographic printing system with an estimated useful life of less than 100 cycles.

However, the prior art negatively chargeable OPC
Also has some drawbacks: 1. A large amount of ozone is generated during the negative corona charging process, which causes environmental problems. This problem has been addressed by installing ozone absorbers such as activated carbon filters and by using contact negative charging instead of corona charging. However, such ozone countermeasures have their own drawbacks and are not advantageous as industrial solutions.

2. The uniformity of the charge pattern obtained by negative corona charging is generally inferior to that of the charge pattern obtained by positive corona charging. The lower the uniformity of the charge pattern, the more noise there is and the lower the definition in the final image.

3. In fine particle toner processes, including dry fine powder processes and liquid toner processes, designers can obtain higher charge stability with positively charged toners than with negatively charged toners. Therefore, positively chargeable OPC ((+) OPC) is preferred for images in which the discharged areas are developed, as in laser printers.

[0011]

It is known that the phthalocyanine pigment powder in a specific form exhibits excellent photoconductivity. Such phthalocyanine pigments have been used as a mixture in a polymeric binder matrix in electrophotographic photoconductors deposited on a conductive substrate. In such phthalocyanine / binder photoconductors, photocharge generation and charge transfer occur within the phthalocyanine pigment particles, while the binder is inactive. Therefore, the photoconductor can be formed of a single layer of phthalocyanine / binder. These single layer photoconductors
Due to the hole (positive charge) mobility of phthalocyanine pigments,
It is known to be a very good positively charged OPC.

In this case, it is not necessary in these single-layer photoconductors to add charge-transfer molecules or to provide a separate charge-transfer layer. The phthalocyanine pigment content is probably in the range of about 10 to 30% by weight in order to be sufficient to perform both the charge generation function and the charge transfer function, in which case the binder content is about 90 to 70% by weight. It is within the range. The single photoconductor layer described above is typically greater than about 3 μm thick in order to obtain the required charge acceptance and resulting image contrast.

Therefore, the first object of the present invention is to show stable electrical characteristics including charge acceptance, dark decay and photodischarge in a high cycle high quality electrophotographic process (+) OPC. Is to provide. Current digital imaging systems, where the write head is an LED array or laser diode, have very high light densities (approximately
100 erg / cm ² ), resulting in about 10 to 30 erg / cm ²
Of light intensity and an exposure time of between a few hundred microseconds and a few milliseconds will place more stringent requirements on the OPC than an optical input copier.

Unfortunately, there are no products in the current market that provide such stable electrical properties. this is,
This is because such (+) OPC exhibits instability when frequently exposed to the corona charging device and the intense light source in the electrophotographic process. The inventor has found that the instability is further increased, subject to the strong absorption, high light intensity and short exposure time required for the laser printing process. This photoconductor instability is shown as a significant increase in dark decay after a relatively low number of laser printing repeat cycles. This instability also manifests itself as a reduction in surface potential after repeated cycles. Such instability causes a recessive change in image contrast, causing problems with reliability of image quality.

Preferably, the desired electrophotographic performance uses a laser diode beam at a frequency of 780 nm or 830 nm passed through an optical system including a beam scanner and a focusing lens, synchronized to 0.05 microseconds for each beam. In case of about 60 to 100V / μm charge acceptance, about 5
Low dark decay below V / sec and at least 90% of surface charge
Can be defined as the photodischarge of.

Acrylic resins, phenoxy resins, vinyl polymers containing polyvinyl acetate and polyvinyl butyral,
Uses conventional binders for phthalocyanine pigments such as polystyrene, polyesters, polyamides, polyimides, polycarbonates, methyl methacrylate, polysulfones, polyarylates, diallyl phthalate resins, polyethylene, halogenated polymers including polyvinyl chloride and fluororesins. When acceptable, acceptable charge acceptance and photodischarge are obtained. However, none of these polymers that give adequate performance with respect to charge acceptance and photodischarge shows the desired stability under the stringent exposure conditions of the LED array or laser diode described above.

Conventional OPC is currently vulnerable to brittle resistance, especially in high speed, high cycle applications using two-component developers containing magnetic carriers and toners, and in applications using durable cleaning blade materials such as polyurethane. Made of a thermoplastic binder that exhibits abrasion resistance. Generally, OPCs with mechanically abrading surfaces exhibit poor electrophotographic properties, low charge acceptance, high dark decay rate, low speed, and low contrast.

A second object of the present invention is to provide an OPC having excellent durability based on mechanical strength, solvent resistance, and thermal stability. The OPC must be mechanically strong to ensure wear resistance in high cycle applications. The OPC must be solvent resistant so that it does not undergo alteration or loss in liquid toner applications. In addition, the OPC can be at various temperatures, or after various temperatures, especially at or after high temperatures, which are typically about 70 ° C. for current laser printers. It must be thermally stable to ensure predictable and repeatable performance.

Also, conventional thermoplastic binders exhibit higher solubility in solvents used in liquid toner applications. For example, the liquid carrier tends to partially dissolve the OPC binder in the wet environment required to obtain very high resolutions in excess of 1200 DPI associated with high end model applications, which results in poor resolution. Bring Further, in aqueous ink printing applications, water adversely affects the conductivity of OPC's made with these conventional binders, with this effect increasing at higher temperatures.

Conventional thermoplastic binders also show significant thermal degradation in electrical properties that are important for electrophotography, which is reflected in reduced charge acceptance, increased dark decay rate and reduced contrast potential.

A third object of the present invention is to use an OPC for a OPC without the need to further provide a cross-linking agent, a cross-linkable copolymer material or a cross-linking catalyst which may adversely affect the life of the OPC in addition to the binder material. To provide a cross-linking binder.

Therefore, these mechanical, related to OPC,
In order to meet the chemical and thermal durability requirements, a unique crosslinkable polymeric binder material must be obtained.

Generally, crosslinked polymers such as epoxy, phenolic resin, polyurethane and the like are known. In the case of fiber-reinforced plastics, for example in the electronics packaging industry, a significant improvement in glass transition temperature (T _g ) is the crosslinking with heat, radiation (electron beam, UV, X-ray etc.) and / or water vapor Obtained by However, for OPC applications, photoconductive components such as charge generating molecules (dyes, pigments, etc.) and charge transfer molecules are vulnerable to heat, high energy irradiation and water vapor used in conventional crosslinking processes, so that common crosslinking It is impossible to apply the principle freely. Therefore, after cross-linking, these molecules may not be present in the cross-linked product in the form that they act as charge generating or charge transfer molecules. This is hydrazone, arylamine,
Whether it is a hole-transporting molecule such as pyrazoline or triphenylmethane, or an electron-transporting molecule such as diphenylsulfone, fluorenone, or quinone,
Or, even when the photoconductor is a single layer or multiple layers, this is why previous attempts at crosslinked photoconductor binders have been unsuccessful. All these attempts result in inadequate compatibility of the transport molecules in the crosslinked binder, resulting in undesirable photodischarge properties.

A fourth object of the present invention is to provide a cross-linking binder for OPC which has excellent adhesion to other polymer layers. In this way, it is possible to make a multi-layer OPC without easily separating and peeling too much at the interface between layers.

Among the conventional thermoplastic binders, polyvinyl butyral (PVB) provides good dispersibility and good film-forming properties for various types of photoconductive pigments in applications in the field of photoconductor technology. Is considered to be the best binder. However, the use of thermoplastic PVB for phthalocyanine pigments in single-layer (+) OPC still leaves the other in terms of photoresponse to 780 nm laser diodes, electrical stability, environmental stability to heat and liquid toners. It does not give superior performance compared to conventional thermoplastic binders.
Further, the use of thermoplastic PVB as a binder for the charge generating layer of a two-layer photoconductor generally involves the use of a charge generating layer (CGL) binder and a charge transfer layer (CTL).
Binders (generally phenyl polymers such as polycarbonate, polyester, polyimide, polystyrene)
It results in poor adhesion due to poor adhesion due to incompatibility between and.

The present invention aims to provide a method of making an infrared sensitive photoconductor of the type that uses a crosslinkable binder for long life applications.

[0027]

The present invention is a self-crosslinking polyvinyl butyral (PVB) binder for OPCs. This binder in non-crosslinked form is sold by Monsanto Co.
From Butvar ^TM and from Sekisui Chemical Co., Ltd. of Japan
Available as Slek ^™ . The inventor has found that it is possible to self crosslink the PVB by simply heat curing the PVB at about 150 to 300 ° C. for about 2 hours. It is believed that other self-crosslinking methods, such as electron beam radiation, ultraviolet radiation, or X-ray radiation, also give similar results to what the inventors obtained with heat. No cross-linking agent, cross-linkable copolymer or catalyst is required to complete this cross-linking.

After self-crosslinking, the above PVB has excellent mechanical durability and excellent solvent resistance. In addition to this,
The glass transition temperature (T _g ) of this self-crosslinking PVB is about 65 ° C.
To about 170 ° C. Furthermore, when the conventional photoconductor pigments are dispersed in this self-crosslinked PVB, they are well dispersed and the resulting OPCs have good charge acceptance, low dark decay and, in general, good It has a light discharge characteristic.

Particularly for applications for (+) single-layer OPC using x-metal free phthalocyanine (xH ₂ Pc) pigments, a binder self-setting process is carried out by a heat curing process at 150 to 300 ° C. 78 when placed under cross-linking conditions
It is observed that a significant photoresponse enhancement is obtained when exposed to a 0 nm laser. In this case, the above xH ₂ Pc-P
It was confirmed that the VB system does not cause a pigment morphological change. The enhanced photoresponse in cross-linked xH ₂ Pc-PVB has not been fully elucidated. However, P after the crosslinking process
It is presumed that it may be related to the reduction of highly reactive hydroxy (-OH) groups in VB. Generally speaking,
The photo-physical process in metal-free phthalocyanine pigments depends largely on the behavior of the lone pair of its N atom. Interactions between the free -OH groups of thermoplastic PVB and these N atoms (eg hydrogen bonds) can limit the generation of free carriers under photoexcited or thermoexcited processes. Further, the present inventor can adjust the -OH content in the device by changing the firing conditions (the firing temperature and the firing time), for example, to enable the balance adjustment between the photoresponse and the dark decay. That is, it was also found that the highest light response can be realized with the lowest dark decay.

The enhanced photoresponse in the (+) monolayer OPC with xH ₂ Pc / self-crosslinked PVB is also observed in the (−) bilayer OPC structure using the self-crosslinked charge generating layer (CGL). This layer also provides a significant improvement in device stability against repeated cycling and environmental changes in heat and humidity.

OPCs with self-cross-linked PVB also show improved adhesion, so that the multi-layer OPCs formed according to the present invention provide improved interlayer bonding and longer economic life.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the accompanying drawings, these drawings include:
FIG. 3 shows a schematic cross section of some embodiments of the invention. O
The PC is provided with a conductive substrate 1 and a photoconductor layer 2. The photoconductor layer 2 can include an independent charge generation layer 2a and an independent charge transfer layer 2b. The charge barrier layer 3 can be optionally placed between the substrate 1 and the photoconductor layer 2. Further, the charge injection barrier layer 4 and the emission layer 5 can be arbitrarily arranged in this order above the photoconductor layer 2. Furthermore, it is possible to use other layers commonly used in OPC (for example, an anti-curving layer, an overcoat layer, etc.).

The conductive substrate 1 may be opaque or generally transparent and may be composed of various suitable materials with the required mechanical properties. Furthermore, the substrate itself may be homogeneous or layered, and if it is layered, it has a conductive surface. Therefore, the substrate can be composed of a layer of non-conductive material and a layer of conductive material containing an inorganic or organic composition. As the non-conductive material, various known resins for this purpose can be used, including polyester, polycarbonate, polyamide, polyimide, polyurethane and the like. The electrically insulative or conductive substrate can be rigid or flexible and can have any of a variety of shapes, such as cylinders, sheets, rolls, seamless flexible belts, etc. Is. The conductive portion of the substrate may be a conductive metal layer that may be formed on the insulating portion of the substrate by any suitable coating scheme, such as vacuum deposition. The conductive layer may be a homogeneous metal. Typical metals include aluminum, copper, gold, zirconium, niobium, tantalum, vanadium, hafnium, titanium, nickel,
Includes stainless steel, chromium, tungsten, molybdenum, etc., and mixtures or alloys thereof.

The photoconductor 2 may be a single layer or two layers. In the case of a single layer, this single layer performs both the charge generation function and the charge transfer function. In the case of two layers, one layer has a charge generation function and the other layer has a charge transfer function.

Any suitable charge generation (photocharge generation) layer 2A
Can be provided on the substrate 1 or the barrier layer 3. Examples of materials for the photogenerating layer include amorphous selenium, trigonal selenium, selenium-tellurium, selenium-tellurium-arsenic, and selenium arsenide dispersed in a thin film-forming polymer material. Inorganic photoconductive particles, such as selenium alloys selected from x and x as disclosed in US Pat. No. 3,357,989.
In the form of metal-free phthalocyanine and phthalocyanine pigments such as metal phthalocyanine (vanadyl phthalocyanine, copper phthalocyanine, titanyl phthalocyanine, aluminum phthalocyanine, haloindium phthalocyanine, magnesium phthalocyanine, zinc phthalocyanine, yttrium phthalocyanine) and squarylium (sq
uarylium), "Monastral Red", "Monastral Viole"
quinacridone, such as the products marketed by Du Pont under the trade names "t" and "Monastral Red Y"
, "Hostaperm orange", "Vat orange 1", "Vat
dibromoanthanthrone pigments such as those marketed under the tradename "orang 3", benzimidazole perylene, and substituted 2,4-diaminotriazines disclosed in U.S. Pat. No. 3,442,781;
st Double Scarlet "," Indofast Violet Lake B ",
"Indofast Brilliant Scarlet", "Indofast Orang
Includes polynuclear aromatic quinones such as those available from Allied Chemical Corporation under the trade name "e", benzofuranone, thiopyrrollopyrole, and the like. It is possible to use a multilayer photocharge generating composition that enhances or reduces the properties of the photogenerating layer of the photoconductive layer. An example of this type of construction is disclosed in US Pat. No. 4,415,639. Other suitable photocharge generating materials known in the art can be used if desired.

The photocharge generating composition or pigment can be included in the resinous binder composition in various amounts. The photogenerating material is preferably included in the range of about 8% to about 50% by weight based on the binder component.

Photoelectric charge generating layer 2A generally has a thickness in the range of about 0.1 micrometer to about 5.0 micrometers, and preferably has a thickness in the range of about 0.3 micrometer to about 3.0 micrometers. Photoelectric charge generation layer 2A
Thickness is related to binder content. In general, the greater the binder content, the greater the layer thickness required for photocharge generation. It is also possible to choose thicknesses outside these ranges if the object of the invention is realized.

Any suitable conventional method may be used to mix the photogenerating layer 2A coating mixture and apply the photogenerating layer 2A coating mixture to the pre-dried substrate 1 or barrier layer 3. It is possible to use. Typical application methods include spraying, dipping, roller coating, wire wound rod coating and the like. Drying of the applied coating to remove almost all of the solvent used in applying the coating may be done by any suitable conventional method such as oven drying, infrared radiation drying, air drying and the like. .

The charge transfer layer 2B can promote the injection of photoexcited holes or electrons from the charge generation layer 2A, and the holes or electrons can be discharged through the organic layer to selectively discharge the surface charge. May include any suitable transparent organic polymeric or non-polymeric material that allows migration of the. The charge transfer layer 2B not only functions to transfer holes or electrons, but also protects the photocharge generation layer 2A from abrasion or chemical corrosion and thus prolongs the operational life of the OPC.
The charge transfer layer 2B has a wavelength (for example, 40
In all cases, it should produce a slight discharge when exposed to light from 0 nm to 900 nm). Generally, the charge transfer layer 2B has a charge generation layer 2A under which most of the incident radiation is located when the exposure is performed through the layer.
In order to ensure that the photoconductor is utilized by the photoconductor, it is transparent in the wavelength range in which it must be used. When used with a transparent substrate,
All light passing through the substrate can expose or erase the image through the substrate. In this case, the charge transfer layer 2B does not need to pass light within the usable wavelength range. The charge transfer layer 2B combined with the charge generation layer 2A is an insulator having an insulation property that does not conduct static charge applied to the upper surface of the charge transfer layer 2B when there is no irradiation.

The charge transfer layer 2B comprises an activating compound or charge transfer molecule dispersed in a normally electrically inactive film-forming polymeric material to render it electrically active. But it's okay. These charge transfer molecules can be added to polymeric materials that are unable to facilitate the injection of photogenerated holes and are unable to move these holes. A particularly preferred transfer layer for use in multilayer photoconductors comprises about 25% to 75% by weight of at least one charge transfer aromatic amine and a polymeric film forming resin in which these aromatic amines are soluble. Includes about 75% to about 25% by weight.

In the case of conventional OPC, any suitable inert binder which is soluble in methylene chloride or other suitable solvent can be used. Typical inert resin binders that are soluble in methylene chloride include polycarbonate resins, polyvinylcarbazoles, polyesters, polyarylates, polyacrylates, polyethers, polysulfones, and the like. The molecular weight can vary between about 20,000 and about 1,500,000. Other solvents capable of dissolving these binders include tetrahydrofuran, toluene, trichloroethylene, 1,1,2-trichloroethane, 1,1,1-trichloroethane and the like.

The thickness of the charge transfer layer is generally about 10 μm.
To about 50 μm, preferably about 20
It may be in the range of μm to about 35 μm. The optimum thickness is about
It may be in the range of 23 μm to about 31 μm.

In the case of the OPC of the present invention, the charge generation layer 2B
Binder resin is self-crosslinked polyvinyl butyral (P
VB). Other layers are also self-crosslinking PV
B can be included.

PVB has the formula:

[0045]

[Chemical 1]

In the above formula, R is alkyl, allyl, aryl with or without conventional functional substituents, l = 50 to 95 mol% m = 0.5 to 15 mol% n = 5 to 35 mol% is there.

The PVB crosslinks simply reduce the PVB to about
It is carried out by heating to 150 to 300 ° C. The firing time depends on the thickness and binder content and may be between a few minutes and a few hours. It is believed that other cross-linking methods, such as electron beam, UV or X-ray irradiation, will give similar results to those obtained using heat. This cross-linking reaction occurs when --OH and --O-- groups from different locations on the same PVB polymer chain or --OH and --O-- groups from different PVB polymer chains react with each other. It is thought that this is due to the formation of cross-linking bonds.

A barrier layer 3 can be applied to the upper surface of the conductive substrate 1. The electron barrier layer 3 for positively charged OPCs allows holes to migrate from the imaging surface of the photoreceptor towards the conductive layer. Load OP
In the case of C, any suitable hole blocking layer capable of forming a barrier can be used to prevent hole injection from the conductive layer to the opposite photoconductive layer. is there. The thickness of this barrier layer may be in the range of about 20Å to about 4000Å, preferably in the range of about 150Å to about 2000Å.

The charge injection barrier layer 4 and the emissive layer 5, which are optional overcoat layers, can be formed of an electrically insulating or slightly semiconducting inorganic or organic polymer. The thickness of these overcoat layers may be in the range of about 2 μm to about 8 μm, preferably in the range of about 3 μm to about 6 μm. The optimum range for this thickness is about 3 μm to about 5 μm.

Crosslinking Test Procedure The amount of crosslinking reaction was investigated indirectly. In our test I, we _first weighed a sample of OPC (M ₁ ), after which the sample was submerged in a dichloromethane solvent bath. The sample was then left immersed in the bath for a few hours and dried at 80 ° C. for 1 hour after immersion. After that, the weight of the sample (M ₂ ) was measured again to determine the difference (M ₁ −M ₂ ). Assuming that the lost portion of the sample was already dissolved in the solvent and was not protected by crosslinking, the formula (M ₁ -M ₂ ) / M ₁ is% crosslinking
Represents

The results of several crosslinking tests on PVB are shown in Table 1 below.

[0052]

[Table 1]

From Table 1 above, it is clear that Sample 2 was 80% self-crosslinked after curing at 200 ° C.

OPC Test Procedure a) Laser Response: A fully ground OPC sample was wrapped around an Al drum having a diameter of 180 mm. The drum was rotated at a speed set at 3 inches per second. This OPC is first charged by corona charging at the start position (0 degree position), then
Exposed to 780nm laser (output 2mW at 20 degrees). 30
Surface potential of the OPC exposed to the laser scan (V
e) and the surface potential (Vo) of unexposed OPC were detected. This Vo value (volt) corresponds to charge acceptance, and the Ve value corresponds to laser response.

B) Life test: Using the same conditions as described above for the OPC sample, "charging, laser exposure, L
A repeated cycle of "ED erase" was performed. Accompany the cycle
Changes in Ve and Vo charging will give information on OPC lifetime. Vo (1) = Vo of the first cycle, Vo (1000)
= Vo of the 1000th cycle.

C) Thermal stability test: Test a and test b were performed under heating condition by incorporating a heater inside the Al drum. Using a thermocouple and a temperature control device,
The set temperature was adjusted.

EXAMPLES Example 1 Investigation of the Effect of Crosslinking on Laser Response and Dark Attenuation Using stainless steel beads (4 mm) and ball mill, 16 g xH ₂ Pc and 84 g polyvinyl butyral (Aldrich Chemical) were used. , 900 g of dichloromethane were ground together for 24 hours. The suspension was coated onto an Al / Mylar substrate using a doctor blade and dried at room temperature for 4 hours. The OPC sample was divided into multiple identical fragments of OPC. These OP
C was calcined in the furnace at different temperatures for different times. Thereafter, the calcined OPC samples were used in tests a, b, c above. The results are shown in Table 2 below.

[0058]

[Table 2]

Compared to samples with a low degree of crosslinking,
Samples with a higher degree of crosslinking give better laser response and lower dark decay.

Example 2 Investigation of Life Test Effect of Crosslinking On some of the OPC samples described in Example 1 above.
A 1000 cycle life test was performed. The results are shown in Table 3 below.

[0061]

[Table 3]

This table reveals that the crosslinked samples have a higher electrical stability than the non-crosslinked samples.

Example 3 Investigation of the effect of calcination time at high calcination temperatures on cross-linking O at temperatures of 225 to 250 ° C. for various calcination times.
Example 1 except that the PC sample was fired
The OPC formulation described in 1. was repeated. Laser response test a) of these OPC samples at room temperature and 55 ° C.
And life test b). In this case the electrical stability of the sample is determined by the ratio DV (RT) = Vo (1000) / Vo (1) measured at room temperature (RT) and DV (55) = 55 ° C by heating the sample. Measured Vo (1000)
/ Vo (1). The results are shown in Table 4 below.
Shown in.

[0064]

[Table 4]

In view of these results, it should be understood that changes in firing time can result in changes in the hydroxy content of the OPC sample. Two
Samples fired at 80 ° C. over time show low laser response and low thermal stability, ie low lifetime. Samples fired at 225 ° C and 250 ° C for 10 to 30 minutes showed improved laser response and improved lifetime and thermal stability. This is believed to be due to the sample being partially cross-linked (especially at the surface). What this means is that the surface contains only a small amount of hydroxy (-OH) or no hydroxy groups compared to most other OPCs. The sample calcined at 250 ° C. for 2 hours contained no hydroxy groups. This resulted in that this particular calcination condition gave a very good laser response but resulted in poor thermal stability and lifetime due to the lack of hydroxy groups in most of the OPC.

Example 4 Preparation of a bilayer OPC containing a crosslinked charge generating layer Using stainless steel beads and a ball mill,
5 g of xH ₂ Pc and 5 g of polyvinyl butyral (PV
B) and 190 g of dichloromethane were ground together for 48 hours. The suspension was applied onto an Al / Mylar substrate using a doctor blade and dried at 80 ° C. for 20 minutes to give a thickness of 0.5 μm. The OPC sample was split into two identical fragments of OPC. One OP
The C pieces were tested by baking at 200 ° C. for a further 2 hours and detecting the insolubility of the layer.

Then 400 g of p-tolylamine and 600 g of
g of polycarbonate (Makralon ^™ ) were dissolved together in 5600 g of dichloromethane. The resulting solution is dip coated onto the top surface of the charge generating thin film prepared above and dried at 135 ° C. for 20 minutes to give a thickness of about 18 μm on the top surface of the charge generating thin film. A charge transfer thin film was formed.

The laser electrophotographic performance of these two samples is shown in Table 5.

[0069]

[Table 5]

The results show that the crosslinked CGL samples show improved stability. Note that these samples were charged by a negative corona charger.

Example 5 Adhesion Test Further, a tensile type adhesion test was conducted on the above-mentioned samples 1 and 2. In this test, a piece of strong adhesive tape was applied to the upper surface of the charge transfer thin film and the adhesive tape was pulled vertically upwards until the charge transfer thin film peeled 1 cm away from the charge generating film. The force required to cause this separation was measured and some of the results are shown in Table 6.

[0072]

[Table 6]

These results show that the self-crosslinked sample 2 has a very large adhesion, which is more than 13 times larger than the uncrosslinked sample 1.

Example 6 IR Spectra FIGS. 5 and 6 show two types of polyvinyl butyral, Butvar ^™ B-76 and B-98 (Monsant), fired at various temperatures.
Ft-IR spectrum of Chemical) is shown.

It is recognized from the above results that in both cases a crosslinked PVB was formed with the reduction of the --OH groups detected at a wave number of 3500 (cm ^-1 ).

While the preferred embodiments of the invention have been illustrated and described above, it is understood that the invention is not limited to the above embodiments, but can be practiced in various forms within the scope of the appended claims. Must be clearly understood.

Embodiments composed of combinations of various constituents of the present invention will be exemplified below. 1. Self-crosslinking polyvinyl butyral binder component.

2. An organic photoconductor for electrophotography,
From a conductive substrate, a binder component containing self-crosslinked polyvinyl butyral, which forms a layer of a thickness of about 1 micrometer or more on the substrate, and a pigment component uniformly distributed throughout the binder component. The photoconductor.

3. The binder component is about 150 to 300
The photoconductor of claim 2 which self-crosslinks upon exposure to heat of ° C.

4. The photoconductor of claim 2 wherein the binder component self-crosslinks upon exposure to electron beam radiation.

5. The photoconductor of claim 2 wherein the binder component self-crosslinks upon exposure to ultraviolet radiation.

6. The photoconductor of claim 2 wherein the binder component self-crosslinks upon exposure to X-ray radiation.

7. The photoconductor of claim 2 further comprising a polymer component that forms an additional layer on top of the layer of binder component.

[0084]

As described above, according to the present invention, PVB after self-crosslinking has excellent mechanical durability and excellent solvent resistance, and at the same time, the glass transition temperature rises. Also, conventional photoconductor pigments are well dispersed in self-crosslinked PVB, and the resulting OPCs have good charge acceptance, low dark decay, and good photodischarge characteristics. Furthermore, OPCs with self-crosslinked PVB show improved adhesion, and multilayer OPCs made according to the present invention have improved interlayer adhesion and longer economic life.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a first embodiment of the present invention.

FIG. 2 is a schematic sectional view of a second embodiment of the present invention.

FIG. 3 is a schematic sectional view of a third embodiment of the present invention.

FIG. 4 is a schematic sectional view of a fourth embodiment of the present invention.

FIG. 5: Polyvinyl butyral Bu baked at various temperatures
It is a graph which shows the Ft-IR spectrum of tvar ^TM B-76 (Monsanto Chemical).

FIG. 6: Polyvinyl butyral Bu baked at various temperatures
3 is a graph showing an Ft-IR spectrum of tvar ^™ B-98 (Monsanto Chemical).

[Explanation of symbols]

 1 Conductive Substrate 2 Photoconductor Layer 2A Charge Generation Layer 2B Charge Transfer Layer 3 Charge Barrier Layer 4 Charge Injection Barrier Layer 5 Emission Layer

Claims (1)

[Claims] 1. A self-crosslinking polyvinyl butyral binder component.